SYNTHESIS OF HIERARCHICAL BEA ZEOLITE BY POST SYNTHETIC SURFACTANT TEMPLATING PROCESS

Zeolites are porous aluminosilicates used as catalysts in several industrial reactions. They have wide applications due to their crystalline structures with intrinsic microporosity (< 2 nm). These intrinsic small porous structure leads to slower transport of bulky species which causes diffusion limitation, unwanted side reactions and deactivation of catalysts. Overall efficiency of the catalysts is therefore reduced. To solve the slow mass transport in zeolite catalysts we incorporate mesopores (2-50 nm) in the framework of zeolites thus forming hierarchical zeolites which are proven as an effective method for addressing the transport issue. Currently two techniques are used for incorporating mesopores –bottom up and top down. In bottom-up method mesopores are created along with micropores during their synthesis, but it is economically impractical because of costly templates and altered synthesis routes. In top-down methods, specifically surfactant templating method is efficient, easy and flexible with respect to incorporation of mesopores, as we can largely vary the process parameters for a wide range of zeolites and control the mesoporosity. This research focuses on surfactant templating of *BEA (Beta) zeolite. The aim is to study how surfactant templating methods differ in aluminum containing *BEA (Al-BEA) and de-aluminated *BEA (D-BEA). D-BEA was synthesized from dealumination of commercial Al-BEA in acidic condition. Both D-BEA and Al-BEA were surfactant templated using a wide range of sodium hydroxide (NaOH) and surfactant concentrations. XRD results assured that the crystal structure of the zeolites can be maintained after the surfactant templating process. N2 adsorption/desorption isotherms were used to characterize textural property of the hierarchical zeolites. It was observed that the BET surface area of D-BEA increased up to 800 m2/g from 500 m2/g with an optimized surfactant templating treatment. NLDFT pore size distribution analysis also confirmed the incorporation of mesoporosity in both Al-BEA and D-BEA samples. It was found that the parent Al-BEA had an external surface area of around 186.9 m2/g which was increased to 438.9 m2/g. Parent D-BEA had an external surface area of around 145.3 m2/g which was increased to 808.4 m2/g after surfactant templating.